Disentangling species and functional group richness effects on soil N cycling in a grassland ecosystem

Xiaorong Wei, Peter B. Reich, Sarah E. Hobbie, Clare E. Kazanski

Research output: Contribution to journalArticlepeer-review

10 Scopus citations


Species richness (SR) and functional group richness (FGR) are often confounded in both observational and experimental field studies of biodiversity and ecosystem function. This precludes discernment of their separate influences on ecosystem processes, including nitrogen (N) cycling, and how those influences might be moderated by global change factors. In a 17-year field study of grassland species, we used two full factorial experiments to independently vary SR (one or four species, with FGR = 1) and FGR (1–4 groups, with SR = 4) to assess SR and FGR effects on ecosystem N cycling and its response to elevated carbon dioxide (CO2) and N addition. We hypothesized that increased plant diversity (either SR or FGR) and elevated CO2 would enhance plant N pools because of greater plant N uptake, but decrease soil N cycling rates because of greater soil carbon inputs and microbial N immobilization. In partial support of these hypotheses, increasing SR or FGR (holding the other constant) enhanced total plant N pools and decreased soil nitrate pools, largely through higher root biomass, and increasing FGR strongly reduced mineralization rates, because of lower root N concentrations. In contrast, increasing SR (holding FGR constant and despite increasing total plant C and N pools) did not alter root N concentrations or net N mineralization rates. Elevated CO2 had minimal effects on plant and soil N metrics and their responses to plant diversity, whereas enriched N increased plant and soil N pools, but not soil N fluxes. These results show that functional diversity had additional effects on both plant N pools and rates of soil N cycling that were independent of those of species richness.

Original languageEnglish (US)
Pages (from-to)4717-4727
Number of pages11
JournalGlobal change biology
Issue number11
StatePublished - Nov 2017

Bibliographical note

Funding Information:
U.S. National Science Foundation, Grant/ Award Number: DEB-9411972, DEB-0080382, DEB-0620652, DEB-1234162; Biocomplexity Coupled Biogeochemical Cycles, Grant/Award Number: DEB-0322057; Long-Term Research in Environmental Biology, Grant/Award Number: DEB-0716587, DEB-1242531; Ecosystem Sciences, Grant/Award Number: NSF DEB-1120064; US Department of Energy Programs for Ecosystem Research, Grant/Award Number: DE-FG02-96ER62291; National Institute for Climatic Change Research, Grant/Award Number: DE-FC02-06ER64158

Funding Information:
This study was funded by programs from the US National Science Foundation (NSF) Long-Term Ecological Research (DEB-9411972, DEB-0080382, DEB-0620652, and DEB-1234162), Biocomplexity Coupled Biogeochemical Cycles (DEB-0322057), Long-Term Research in Environmental Biology (DEB-0716587, DEB-1242531), and Ecosystem Sciences (NSF DEB-1120064) Programs, as well as

Publisher Copyright:
© 2017 John Wiley & Sons Ltd


  • CO elevation
  • N enrichment
  • net N mineralization
  • plant N pools
  • plant diversity
  • soil inorganic N pools


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